The .NET Framework is a software development platform created by .Microsoft that allows developers to build and run applications on Windows. It provides a large library of pre-coded solutions, known as the .Base Class Library, which simplifies the development process by offering ready-to-use functions for common tasks. The framework supports multiple programming languages, including .C# and .VB.NET, enabling developers to choose their preferred language while still being able to use the same libraries and tools. It also includes the .Common Language Runtime (CLR), which manages the execution of applications, ensuring they run smoothly and securely on the Windows operating system.